ADDITIVES FOR HEAVY CONCRETE BASED ON INDUSTRIAL WASTE FROM CHEMICAL INDUSTRIES

Abstract

The effect of a complex additive containing superplasticizer C-3 on the properties of heavy concrete has been investigated. The efficiency of the plasticizing action of the specified additive at the stage of preparation of the concrete mixture and subsequent molding of concrete products has been revealed. It is proved that at the stage of concrete hardening, the investigated additive promotes to the formation of a more homogeneous colloidal-crystalline structure and the formation of dense crystalline hydrate complexes of cement stone by the time of completion of concrete hardening. The objects of investigation were samples of grade B22.5 concrete without additives; containing a monoadditive - superplasticizer S-3; containing the complex additive. When designing the composition of additives for heavy concrete, we proceeded from the fundamental provisions of construction science that the complexity of the action of additives lies in the optimal combination of two main opposite processes in time and volume of the concrete matrix. The use of the caprolactam oligomer synthesized in the course of this investigation makes it possible to solve the problem of involving concentrated wastes of caprolactam production in the production turnover. The obtained caprolactam oligomers can be used in construction as plasticizers of concrete mixtures, as inhibitors of corrosion of steel reinforcement in the production of reinforced concrete products. Water-soluble oligomers of caprolactam, which reduce the time of dissolution of the superplasticizer C-3 and the dispersion of low-temperature catalyst in the volume of the concrete mixture being mixed, were synthesized. It was found that in the presence of the oligomer caprolactam in an amount of 10 to 20% of the mass. the dissolution rate of S-3 superplasticizer in water at a temperature of 20-21 °C increases by 2.0-2.2 times. This contributes to a better mixing of the components of the concrete mixture, primarily to improve the dispersion of the complex additive in the volume of the concrete mixture. The caprolactam oligomer used in this research work is an effective water-soluble wetting agent for the surface of particles of cement, sand, and crushed stone, which is very important for activating hydration and sorption processes during mixing of a concrete mixture. The increased wetting properties of the caprolactam oligomer are characterized by a wetting angle of 19.6 °.